The present invention relates to the chemoprophylaxis of colorectal cancer with combinations of a cyclooxygenase (COX) inhibitor, vitamin D3 including analogues and metabolites thereof and/or calcium. In a further aspect the invention relates to a method for reducing the effective dosage of ASA in a chemoprofylactive treatment of colorectal cancer in a human by co-administration with a non toxic dosage of a vitamin D3 including analogues and metabolites thereof and Ca in the form of a combination dosage. In a still further embodiment the invention relates to the use of a cyclooxygenase (COX) inhibitor, a vitamin D3 and calcium together with a pharmaceutically acceptable carrier for the preparation of a medicament for preventing the initiation and/or progression of colorectal cancer in a human. The invention also relates to such a pharmaceutical medicament.
Colorectal cancer (CRC) is one of the leading cancer forms in the Western world (1.3 million per year and over 600,000 annual deaths). In Denmark, the incidence is approximately 65 per 100,000 inhabitants and correlates to age. Concurrently with a fall in tobacco smoking in Western industrial countries and an increased life expectancy, CRC is expected to become the most frequent solid cancer over the next decades.
The great majority of CRC cases are sporadic cancers, for which it is not possible to establish a genetic disposition. Effective CRC prevention in well-defined risk groups would have a significant effect on population health.
In the average population the lifetime risk of getting CRC is 6 per cent, and the risk of dying from the disease is 3 per cent (1,2,3). In first-degree relatives of patients with CRC, the risk is several times higher. In rare cases, the CRC disposing factors are hereditary non-polyposis colorectal cancer (HNPCC), where it is possible to establish the presence of mutations in mismatch repair genes, familial adenomatous polyposis (FAP, mutation in the APC gene), or inflammatory bowel diseases (ulcerative colitis and Crohn""s disease), these factors accounting for 5 to 15 per cent in all.
There is no doubt that foods are the most important causal factor, including animal proteins and fats, which the Western world is increasingly eating in excess amounts instead of cereals, fruits and vegetables. The incidence of CRC is increasing, but it is only half the magnitude among vegetarians as among meat-eaters (4). The progress made during the last decades within surgical techniques, adjuvant treatment, etc, has not lowered mortality to any mentionable degree. CRC screening means tracing cancers at an early stage and removing intestinal polyps, but so far, however, studies have not shown screening to reduce the incidence. The overall five-year survival in Denmark is approximately 30 per cent and depends on the stage at the time of diagnosis. Approximately 25 per cent of the patients have disseminated cancer at the time of diagnosis and are beyond a cure. Three fourths of CRC patients undergo surgery intended to cure; nevertheless, 50 per cent of these patients die within five years because of recurrence.
With the choices and results of treatment known today, only effective prophylaxis will be able to reduce CRC morbidity and mortality (3,5) in a decisive manner.
In recent years, focus is very much on cancer prophylaxis, in acknowledgement of the fact that surgery mostly does not suffice as the only modality and that most cytotoxic regimens are ineffective against solid tumours.
The term chemoprophylaxis covers the use of pharmacologically active, non-cytotoxic agents or naturally occurring nutrients that protect against the emergence and development of clones of mutated, malignant cells.
In 1994, to analyse existing data and to initiate new studies, the National Cancer Institute, USA, established a Chemopreventive Branch. The NCI-CB has concluded that CRC is an attractive target for cancer chemoprophylaxis, since it is a frequent cancer with a high mortality. However, no acceptable treatment is available.
A well-defined multistage carcinogenesis has been mapped with well-defined precursors in the form of colorectal adenomas, and the groups at risk are also well defined.
Some studies have pointed to an inverted correlation between the individual intake of non-steroid anti-inflammatory drugs (NSAID), and of calcium and vitamin D3 and the risk of developing CRC. The studies in question are animal experimental models of colorectal carcinogenesis, prospective studies of patients with FAP and epidemiological studies taking the form of retrospective case-control studies and prospective cohort and interventional studies (6-17). In conclusion, 21 of 23 epidemiological studies have shown that regular use of NSAIDs reduces the risk of CRC by up to 50 per cent (18). However, data are not clear regarding dosage and duration of use. The most frequently studied drugs are acetylsalicylic acid, sulindac, piroxicam and indomethacin.
A few review articles and editorials have been published which find the results interesting, but existing data have neither led to any recommendations proper nor proved any clinical significance (12). This is primarily because of the well-known undesirable effects of NSAIDs and the acknowledgement that the strongest evidence of the effect of these agents does not exist, ie, prospective, randomised double-blind trials in human populations.
The American Cancer Society has concluded that current data from epidemiological, clinical, pharmacological and toxicological studies show that acetylsalicylic acid protects against CRC development (13), and the FDA is currently assessing whether acetylsalicylic acid taken alone should be approved as chemoprophylaxis of CRC, or whether further phase III studies will be necessary.
Animal experimental data draw a promising picture of pharmacologically active drugs that, with different mechanisms of action, appear to be effective chemoprophylactic agents. However, individual epidemiological studies of calcium and vitamin D (or milk products) in relation to CRC are inconsistent. Out of 13 studies of calcium (nine case-control and four cohort studies), eight show a significant inverse correlation, three studies report insignificant correlation, whereas two fail to show any correlation.
Out of five epidemiological studies (three cohort studies and two case-control studies) of the impact of vitamin D on the CRC risk, two show a significant inverse correlation, whereas the rest have no significance.
The sequence of epithelium-adenoma-carcinoma is a process taking many years (5 to 10 years). CRC differs from many other cancers in as much as mutations in cell-cycle regulating genes and gene products are rarely seen. CRC is characterised by mutations in critical tumour suppressor genes (APC, DCC, p53, MCC) and oncogenes (K-ras) and upregulation in growth factors (especially the EGF-family) and enzymatic activity (especially cyclooxygenase).
In spite of CRC being a frequent cancer form, its incidence is only 65 per 100,000 inhabitants, and a clinical-controlled study with the endpoints being invasive cancer and cancer-related deaths would require enrolment of tens of thousands individuals, and it would run for several decades and require astronomical financial resources. Healthy individuals do not feel impelled to participate in scientific studies including long-term medicine intake, and the results of any such studies would be subject to confounding.
Over 95 per cent of CRC develop from adenomas, which are accepted CRC precursors in scientific studies of humans and in animal experiments. Other biomarkers include genomic changes (mutations, etc), aberrant crypt foci (ACF), ornithine decarboxylase activity, cyclooxygenase activity and the prostaglandin level in mucosa, which are used as intermediary endpoints.
Colorectal carcinogenesis and Calcium:
In the Western world, the daily average intake of calcium is substantially below the recommended dietary allowance (RDA) of 800 to 1200 mg/day, increasing to 1500 mg/day for the elderly. In Western countries, each adult has an average daily intake of 750 to 850 mg of calcium (14).
Approximately 30 per cent of dietary calcium is absorbed from the intestinal canal, and vitamin D3 stimulates the absorption. The absorption is both transcellular (at low dietary calcium content) and paracellular. The residual amount of calcium in the intestinal lumen binds free fatty acids and secondary bile acids by formation of insoluble soaps and reduces the local irritant effect of these acids in the colon.
Deoxycholic acid (DCA) in particular, which produces epitheliolysis in the epithelial surface of the colon, is considered to be the most carcinogenic and mitogenic of the secondary bile acids (15). Epitheliolysis induces potent proliferation in the crypts, probably as a result of exposure of the basal membrane. In the activated phase (S phase), the cells are more sensitive towards carcinogens like DCA, free fatty acids, etc (16). In vivo the harmful effect of 5 mM DCA can be prevented by increasing the Ca concentration in the intestinal lumen from 0 to 4 mM.
In several cases, the results of case-control studies and cohort studies have shown a significant correlation between a high dietary calcium level and a reduction in the risk of CRC development. However, the results are not unambiguous, although large volumes of data from animal experimental studies all point in the same direction (14). One prospective study shows a significant reduction in the rate of polyp recurrence and a significant increase in cancer-related survival following CRC surgery at calcium supplements (calcium carbonate 2 g/day (17).
The formation of insoluble calcium soaps is still considered to be the most important mechanism of the cancer preventive action of calcium, but in recent years focus has increasingly been directed at the central role of calcium in intracellular signal transduction. Calcium is a key factor in maintaining normal cell membrane function, and calcium flux over the cell membrane plays a central role in mediating intracellular signal transduction, which regulates multiple cellular functions. Furthermore, the expression of cellular surface cadherins, which is necessary to maintain intercellular contact, depends on the presence of calcium. Particularly on colon cancer cells the expression of cadherins correlates with the rate of differentiation and the clinical outcome (19).
Reduction of calcium concentration in intercellular fluid lowers cell response to growth regulating factors and reduces the permeability of cell membranes. When the calcium concentration is reduced, the rates of proliferation and dedifferentiation increase.
Calcium contributes to regulating all cell division and cell differentiation phases, primarily through activation of various protein kinases (cAMP-dependent kinase, Ca-calmodulin-dependent protein kinases, protein kinase C) (20,21). Calcium suppresses ornithine-decarboxylase, a tumour-promoting enzyme (14) and reduces the number of K-ras mutations in colonic epithelium stimulated with the carcinogen 1,2 dimethylhydrazine (22). K-ras mutations are one of the early genomic changes in the carcinogenesis. K-ras mutations occur in approximately 85 per cent of adenocarcinomas and approximately 55 per cent of adenomas, but ras mutations exist even in up to 50 per cent of ACF.
Elevated calcium values produce increased differentiation of epithelial cells with concurrent growth suppression, but neoplastic colonic epithelial cells presumably lose their calcium response at one of the late stages of the epithelium-carcinoma sequence (16).
Stimulation with carcinogens at the preneoplastic stage produces luminal proliferation of the colon crypt proliferating cells, an increased proliferation ratio and an increased incidence of ACF, which is also seen in individuals with an elevated risk of colon cancer (HNPCC and FAP patients). At calcium administration, cells in the crypts can be converted to a normal proliferation ratio and normal geographical distribution of non-dividing cells in the luminal two thirds of the crypts and proliferating cells at the bottom of the crypts (23).
Montoya R. G. et al, xe2x80x9cChemoprevention of gastrointestinal cancer.xe2x80x9d CANCER AND METASTASIS REVIEWS (1997) 16/3-4 (405-419) discloses several compounds used for the prevention of colon cancer. There is no mentioning of vitamin D3 and the reference to Ca relates to the theory concerning formation of insoluble calcium soaps.
WO 96 41645 discloses the use of COX2 inhibitors for use in the treatment of inflammation.
Pence B. C. et al: Experimental chemoprevention of colon carcinogenesis by combined calcium and aspirin (Meeting Abstract), Proc. Annu Meet AM Assoc Cancer Res (1994). Vol. 35, pp A3719. ISSN: 0197-016X describes that tumour burden was lowest in groups fed Ca or ASA during promotion only. Supplementation during progression was less effective.
Sokoloski, John A. et al: Introduction of the differentation of HL-160 romyelocytic leukemia cells by nonsteroidal anti-inflammatory agents in combination with low levels of Vit D3; Leuk. Res (1998), 22(2), 153-161, 1998. This article discloses that D3 has an increasing effect on NSAID; however, only derivatives with receptor-binding properties have this effect and D3 analogues without receptor-binding effect and with the Ca increasing effect do not have this increasing effect on the NSAID. The study was performed with leukemia cells.
Colorectal carcinogenesis and Vitamin D3:
Vitamin D3 (D3) increases serum calcium by furthering the absorption of calcium and phosphate from the intestinal canal and mobilising calcium from bones. D3 is present in food; it is formed by ultraviolet radiation of 7-dehydrocholesterol, a provitamin present in human skin and in fatty tissues in many animals. D3 metabolises by successive hydroxylation, first in the liver, into 25-hydroxycholecalciferol, and then in the kidneys to 1,25 dihydroxycholecalciferol (1,25DHC) or 24,25DHC, which are the hormonally active metabolites of D3 (1,25DHC greater than 24,25DHC).
In addition to its anti-oxidative effect, 1,25DHC resembles steroid hormones in its chemical structure and mechanism of action as 1,25DHC passes the cell membrane and binds to a specific cytoplasmatic receptor protein. This hormone-receptor complex is activated during translocation into the cell nucleus where it binds to DNA and initiates mRNA transcription and protein synthesis. In the nuclear membrane receptors for 1,25DHC are situated (high affinity nuclear vitamin D receptors, VDR), which contribute to regulating the calcium flux over cell membranes (17).
1,25DHC modulates signal transduction, inhibits proliferation and DNA synthesis, modulates c-myc, c-fos and c-jun oncogenic expression, induces differentiation and presumably apoptosis. VDRs have been identified both in normal colonic mucosa and in colorectal carcinomas (24). 1,25DHC increases intracellular calcium and stimulates various protein kinases, 1,25DHC stimulates transcription of the calbindin D gene in colonocytes, which is believed to increase transcellular calcium absorption.
A potent upregulation (300-400 per cent) of VDR takes place in neoplastic colonocytes; this can be interpreted as an adaptive response to tumour cell growth, by which the cell increases its differentiation potential. This response disappears at more advanced stages of the disease ( greater than T3), where it is assumed that the vitamin D defence mechanism becomes inactivated (25).
In vitro, 1,25DHC inhibits the growth of human colon cancer cell lines (LoVo) including CEA-producing cell lines. In vivo (mice), 1,25DHC can suppress growth of solid, human xenografts (17,26). A few cohort studies of human populations have shown a significant reduction in the risk of developing colorectal cancer at intake of vitamin D3 (or its active metabolite 1,25DHC), resulting in serum concentrations above 20 ng/ml (6,7).
RDA for vitamin D3 is 10 xcexcg/day increasing to 20 xcexcg/day in elderly women without oestrogen substitution (6,7,27). The recommended dose of 1,25DHC is 0.01 xcexcg/kg BW three times a week. In osteoporosis studies, 0,75 xcexcg/day has been shown to induce hypercalcaemia.
New synthetic D3 analogue preparations have 100-200 times the antiproliferative effect and effect on differentiation and only 0.5 times the hypercalcaemic effect of 1,25DHC.
Two NCI-CB sponsored studies of 1,25DHC 0.5 xcexcg or D3 400 IU and calcium carbonate 1500 mg have been initiated in 1994.
It is known from studies of bone mineral turnover that vitamin D and calcium are mutually dependent factors, and this has proved to be the case also in the regulation of cell division and cell differentiation.
Colorectal carcinogenesis and cyclooxygenase inhibitors (acetylsalicylic acid (ASA) and other NSAIDs) and CRC:
The regulating effect of cyclooxygenase inhibitors (COX inhibitors) on the colonic epithelium has been investigated in connection with the treatment of chronic inflammatory intestinal diseases and FAP.
A cancer preventive effect of COX inhibitors has not been identified in detail at the level of molecular biology, but it is considered to be related to the impact of these drugs on arachidonic acid metabolism and prostaglandin synthesis via blocking of cyclooxygenase enzymes (COX).
Two isomeric forms have been identified: COX1 and COX2:
COX1 is the constitutive form. In the upper gastrointestinal tract it affects the protection of mucosa by inducing bicarbonate secretion and mucin production primarily through prostaglandin E (PGE), which is the quantitatively dominant product of the COX1 turnover of arachidonic acid. COX2 is an inducible form. It is particularly induced by inflammatory stimuli, and it catalyses the formation of proinflammatory cytokines, including PGE2 and PGFxcex1, which strengthen the mutagenic effect of carcinogens by proliferation induction, suppression of the immune system and stimulation of angiogenesis. PGE2 exerts its inhibitory effect via negative feedback T-cell proliferation and lymfokine production.
Arachidonic acid (AA, 5,8,11,14-eicosatetraenoic acid) originates from the cell turnover of phospholipids (PL) located in the cell membrane. AA is primarily liberated from PL by hydrolysis of the ester binding that binds AA to PL. In most cell types this occurs by direct activation of the enzyme phospholipase A2. The phospholipase A2 activity constitutes the common factor regulating the rate of AA liberation, and thus the rate of production for all eicosanoids (PG, prostacydins, thromboxanes and leukotrienes).
AA metabolises via the COX pathway to eicosanoids which stimulate cell division, as it is seen in inflammatory conditions, or via the lipoxygenase pathway to hydroperoxides (HPETE) and hydroxy compounds (HETE). The third pathway for arachidonic acid metabolism is via cytochrome P450 to HETE and EET (epoxyeicosatrienic acid). It has been shown that blocking of the lipoxygenase activity inhibits growth-factor-induced colonic tumour cell proliferation (28).
The COX inhibitor ASA (aspirin and others) and its metabolite salicylate block the formation of PG from AA by irreversible acetylation of COX (29), denying AA access to the active part of the enzyme. The COX activity can only be re-established by production of new COX molecules, and therefore cells without protein synthesis, such as platelets, are not capable of resuming COX activity. The main chemopreventive effect of ASA is deemed to be COX2 inhibition (30), which results in metabolising of AA via a lipoxygenase pathway to 15-HETE (leukotriene with anti-inflammatory and antimitogenic effects).
Most other NSAIDs (piroxicam, sulindac and indomethacin) block COX in a reversible and dose-dependent manner, and ASA is therefore a more potent PG inhibitor. As will be apparent from the above, there are several mechanisms of action, and the PG cascade also depends on the calcium-regulated signal transduction system (21).
Several classic carcinogens are used as electron donors during the COX reaction, and they are activated by this reaction (high DNA affinity). Among them are polycyclic aromatic hydrocarbons, aflatoxins, halogenated pesticides, aromatic amines and phenol compounds. Thus, COX activates potential carcinogens into active DNA harmful metabolites.
In vitro studies show that most NSAIDs have an antiproliferative effect on human colon cancer cell lines (Ht-29, SW-80, DLD-1) (31).
In vitro studies also show that although the NSAID effect on the PG-synthesis is eliminated (for instance by the use of sulindac metabolites without COX inhibition), the growth of human colon cancer cell lines is nevertheless inhibited. This points to several mechanisms of action, including the ability significantly to induce apoptosis (28,32), and modulation of transmembrane calcium flux and intercellular junctions (33).
NSAID has been shown to inhibit several endonucleases; these are enzymes that cleave DNA molecules. Presumably they play a central part in the genomic instability which is one of the characteristics of colorectal multistep carcinogenesis (32). Other molecular biology mechanisms are discussed in detail in (35).
An interesting point is that, contrary to other NSAIDs, ASA has been shown to inhibit proliferation and lumen formation in cocultivated normal colon epithelial cells (carcinoma cells in compartment 2). This is taken as an expression of inhibition of the growth promoting signals of carcinoma cells. Other areas in which ASA differs from other NSAIDs are irreversible COX inhibition, lower plasma binding (approximately 50 per cent as compared to approximately 90 per cent).
Human colorectal neoplasms, both adenomas and adenocarcinomas, have been found to produce large amounts of PG, especially of the E type (31,36), and precisely COX2 activity has been found to be accentuated 2 to 50-fold in 85 to 90 per cent of colorectal carcinomas (35). Particularly APC loss of heterozygocity (LOH) is believed to stimulate COX2 expression at an early stage of neoplastic development in both epithelial and stroma cells. However, it may precisely be the stromal COX1 activity that stimulates the expression of various angiogenetic factors (VEGF, bFGF and TGFxcex21).
Other proneoplastic effects of COX are the change of TGF-beta from an anti-proliferative growth factor to a pro-proliferative growth factor and reduced intercellular and cellular-stromal contact/communication, thus promoting angiogenesis and metastasis. These properties of COX suggest that inhibitions of both isoforms may have important effects against CRC (38).
In itself, one of the three domains of the COX molecule (COX domain, EGF-domain and membrane binding motif) resembles the epidermal growth factor (the ligand for the EGF receptor is also TGFxcex1). For this reason a possible inactivation of the entire domain would be interesting in an attempt to achieve optimum prophylaxis.
Several major epidemiological studies of COX inhibitors in the form of cohort studies, case-control studies and prospective interventional studies have shown a significant preventive effect (reduction of relative risk of 40 to 50 per cent) particularly of ASA on CRC after long-term (2 to 10 years) therapy in the doses used to prevent ischaemic heart disease (11-13, 3942). In a cohort of patients with ulcerative colitis, a relative risk reduction of 0.38 (0.2 to 0.7) has been found following only 3 months of sulphasalazine therapy.
Animal trials have been able to demonstrate a significant protective effect (50 to 60 per cent) of for instance indomethacin and piroxicam in rats exposed to the carcinogen dimethylnitrosamine or azoxymethane (methylazoxymethanol) (43-46).
The most frequent undesirable effects connected with long-term administration of NSAIDs are gastroduodenal ulceration and bleeding because of low PG and thromboxane A2 levels in the gastrointestinal tract. PG stimulates mucin production and bicarbonate secretion, and thromboxane A2 indicates platelet aggregation. These complications are primarily related to inhibition of the constitutive COX1 enzyme.
Undesirable effects and complications primarily relate to the use of NSAIDs as analgesic or anti-inflammatory agents in significantly higher doses, but they are potential sequels after long-term use also in lower doses.
A review of 16 cohort studies and case-control studies showed that the risk of developing severe NSAID-induced gastrointestinal undesirable effects amounts to 2 to 4 per cent a year at analgesic and anti-inflammatory daily doses (14). In low-dose aspirin prophylaxis of cardiovascular disease the relative risk-reduction in relation to stroke, acute myocardial infarction and/or cardiovascular death was found to be approx. 25% (47).
The Physicians"" Health Study (325 mg of acetylsalicylic acid qod) found that, in addition to a significant reduction of the risk of acute myocardial infarct, there were significantly more cases of melaena and epistaxis than in the placebo group, but of neither cerebral haemorrhage nor unspecific gastrointestinal bleeding (including haematemesis) (39).
There exist numerous data on the pharmacokinetics and toxicity of COX inhibitors, especially regarding ASA. The FDA has found that for instance acetylsalicylic acid is a safe and efficient anti-inflammatory and analgesic agent and well suited for over-the-counter sales. No further toxicological studies are necessary to assess the usage of acetylsalicylic acid in chemoprevention (48-49).
The carcinogenesis in colorectal cancer involves a number of genetic changes and epigenetic factors such as increased expression of growth factors and suppression of growth inhibitors, which does not necessarily imply underlying mutations (but which for instance occurs at increased COX expression). Data from epidemiological studies and animal trials show that vitamin D3 and calcium may be pharmacologically active when used as chemoprophylaxis of CRC. However, the effect is moderate. Some epidemiological studies in human populations indicate a reduction (40 to 50 per cent) of the relative cancer risk in populations using ASA continuously; there is not, however, consensus as to the dosage and duration of treatment. The risk-reduction in relation to CRC could be twice the risk-reduction of cardiovascular events.
No prospective, randomised, double-blind studies exist. Studies of cancer chemoprophylaxis are extremely expensive, since they perforce have to include a very high number of individuals and run for years if the study endpoints are to be invasive cancer and cancer-related mortality. For these reasons there is an increasing tendency towards relying on epidemiological studies of intermediary endpoints (eg, polyps, ACF, etc), animal trials of genetically engineered or carcinogenically stimulated animal populations and biological models for examining different biomarkers (mutations, growth factors, etc).
According to the present invention, the CRC preventive effect of the following combination of preparations manifests itself by a significant reduction of the incidence and overall morbidity and mortality of colorectal cancer. To achieve this effect, however, it is believed to be important to take the preparation consistently as prophylaxis over a long time (probably more than one year), exactly as for the prevention of ischaemic heart disease and osteoporosis.
By combining ASA with 1,25DHC (or an analogue preparation) or with calcium, an additive or synergistic effect is achieved, so that the amounts of the individual drugs are presumably reduced and the toxicity thereby reduced to a negligible level. In a preferred embodiment, ASA is combined with both 1,25DHC (or an analogue preparation) and calcium.
According to the present invention, a surprising effect may be obtained by a combination dosage comprising individual drugs which exert their effects on specific areas of the carcinogenesis: modification of signal transduction and expression of oncogenes, reduction of carcinogenic impact on the colonic epithelium and intracellular and intercellular signal transduction, COX inhibition and probably apoptosis.
In a further aspect of the invention, the incidence of undesirable gastrointestinal effects with COX inhibitors can be reduced or eliminated by prior eradication treatment of patients testing positive for Helicobacter pylori, who have been tested before initiation of chemoprophylaxis with a urease breath-test.
In a preferred embodiment, the individual subject to be treated is a mammal, preferably a human which due to underlying disease or a genetic defect is in risk of developing colorectal cancer such as: HNPCC patients, polyp patients, patients with a history of CRC. In addition, individuals over 50 years, who are first-degree relatives of patients with colorectal cancer (risk of developing CRC 2 to 4 times increased (12 to 25 per cent).
For first-degree relatives of individuals with CRC diagnosed before the age of 50 years or for individuals with two first-degree relatives with CRC, the risk increases 4 to 6 times (24 to 36 per cent) regardless of age.
For carriers of HNPCC mutations, the risk of CRC is 75 per cent at the age of 65 years and the risk of metachronous cancer is 45 per cent ten years following resection of the primary tumour.
For patients with chronic inflammatory intestinal diseases (ulcerative colitis and Crohn""s disease), the risk increases 4 to 25 times (lifetime risk 12 to 75 per cent in patients not treated with surgery after more than ten years of illness) depending on the dissemination and duration of the disease.
Accordingly, in the use and method according to the present invention, the preferred embodiment is one wherein the human is selected from the group being in risk of development of colorectal cancer due to being a first-degree relative to a patient with colorectal cancer, and/or because he carries the gene(s) for hereditary non-polyposis colorectal cancer (HNPCC), and/or has familial adenomatous polyposis, colorectal adenomas and/or an inflammatory bowel disease such as ulcerative colitis or Crohns disease.
The preparations could be combined as follows:
15 500 mg of Calcium (calcium carbonate 1250 mg) and/or
0.5 xcexcg of 1,25DHC (or a vitamin D3 400 IU or D3 analogue, eg, 0.25 xcexcg of calcitriol or 0.005 xcexcg of calcitriol/kg BW) and
75 mg of ASA or an analogous reversible or irreversible COX2 inhibitor
The main requirements for a preparation designed for chemoprophylaxis include: low price, high compliance and ultra-low toxicity; it is assumed that by adding 1,25DHC and calcium, the amount of COX inhibitor (ASA) can be reduced, so that the ASA-related undesirable effects can be reduced to a negligible level without reducing its action. For acetylsalicylic acid, the undesirable effects following long-term use have made the FDA hesitate before approving acetylsalicylic acid as chemoprophylaxis of CRC.
Preparations with specific action in the colon, such as for instance 5-ASA, may turn out to be appropriate, possibly in combination with mucosa-protective agents.
ASA and other NSAIDs are approved for over-the-counter sales for analgesic and anti-inflammatory use. Similarly, combination preparations containing D3 and calcium (for instance calcium carbonate 1250 mg=calcium 500 mg+D3 400 IU) are sold over-the-counter for osteoporosis prophylaxis.
At first, in vivo studies of the effect of the above have been carried out in the form of animal experiments with the Institute for Toxicology of the Danish Veterinary and Food Administration (DVFA). The results of the studies are shown in Table 1.
Apart from the chemopreventive effect on CRC chemoprevention from the use of a combination of a cyclooxygenase inhibitor, vitamin D3 or an analogue or metabolite thereof and calcium can also be expected on lung cancer carcinogenesis, urinary bladder cancer carcinogenesis and gynaecological cancer carcinogenesis.
In human and in animal studies, the first steps in the multistep carcinogenesis characterizing cancer development in lung mucosa, urinary bladder mucosa and mucosal tissues of the reproductive system (the adenoma-carcinoma sequence which results in the formation of adenocarcinomas) have many identical aspects to colorectal cancer with regard to pathology, involved genetic changes (mutations) and down-stream effects hereof irrespective in which of the above organs they arise.
Mutual events in molecular biology during carcinogenesis in the respiratory tract, gastrointestinal tract, urinary tract and reproductive system are seen in a range of different cellular mechanisms:
Genetic changes during early carcinogenesis: APC mutations and beta-catenin mutations (53, 54), DNA hypomethylation (55), p53 mutations (during promotion progression)
Down-stream effects on growth-promoting oncogenes and growth factors: myc and ras upregulation (56), EGF overexpression (57)
Down-stream effects on growth-inhibiting tumour suppressor genes and growth factors: reduced levels of expression of TGF-beta (58)
Down-stream effects on enzyme expression and metabolism: COX2 overexpression (59, 60, 61, 62), COX1 overexpression (63), increased PgE(2) synthesis (57, 63)
In animal studies on lung cancer, non-steroidal anti-inflammatory agents (NSAID) are shown to counteract the carcinogenesis initiated by the lung-tumour producing chemicals (64).
Accordingly, the scope of the present invention also encompasses methods of treatments similar to the methods of treatments disclosed with respect to colorectal cancer which methods are directed towards chemoprevention for other cancers, such as lung cancer carcinogenesis, urinary bladder carcinogenesis and gynaecological cancer carcinogenesis, and pharamceutical compositions similar to the pharmaceutical compositions disclosed for colorectal cancer for the use therefor. To investigate the chemopreventive effect of the combination of a cyclooxygenase inhibitor, 1,25 Dihydroxycholecalciferol and calcium, research protocols are developed to conduct animal experimental trials using appropriate rodent models of chemically induced carcinogenesis well known to the person of skill in the art. The experimental rodent models are attractive because a substantial overlap exists between man and mouse/rat in the genetic alterations thought to be responsible for tumourigenesis. An example of such a trial is a trial using the A/J mouse lung cancer model wherein the carcinogen stimulation is provided by a benzpyrene product delivered by a gastric tube which study runs for 30 weeks with various combinations of ASA, 1,25 DHC and calcium. The endpoints are precursors lesions such as atypical adenomatous hyperplasia of the lung.